A stepping motor damping system

ABSTRACT

Method and apparatus for electronically damping a stepping motor to prevent the rotor from oscillating in advancing from position to position. The electronic damping includes digital circuits constructed and defined for advancing the rotor from position to position and while advancing, energizing all of the stator windings for a time interval less than the time period required to advance the rotor from position to position and yet of sufficient time duration to prevent the rotor from hunting when it arrives at its new position.

United States Patent Milek 1 May 2, 1972 541 STEPPING MOTOR DAMPING3,514,680 5/1970 Williams ans/13s SYSTEM 3,466,520 9/l969 Aylikci etal... v.

3,385,984 5 1968 OR ..3l8 US [72] Inventor: Donald L. Mllek, Seal Beach,Calif. egdn [73] Assignee: Ex-Cello-O Corporation, Detroit, Mich.Primary ExaminerG Rv Simmons Filed June 9 I970 Attorney-Christie, Parker84 Hale [2i] Appl. No.: 45,172 [57] ABSTRACT Method and apparatus forelectronically damping a stepping 1 /6 5 motor to prevent the rotor fromoscillating in advancing from v t a v a a 4 -H02k 37/00 position toposition. The electronic damping includes digital [58] held Search"318/696, 254; circuits constructed and defined for advancing the rotorfrom 310/49 position to position and while advancing, energizing all ofthe 56 R f d stator windings for a time interval less than the timeperiod 1 e arenas required to advance the rotor from position toposition and yet UNITED STATES PATENTS of suft'lcient time duration toprevent the rotor from hunting 225 9/1969 0 R 318/138 when it arrives atits new position. 3,465, egan 3,345,547 lO/l967 Dunne ..3 l 8/l 38 11Claims, 4 Drawing Figures CZOCK PUL SE GENEPA TOR -25- l SOURCE OFDl/PEC TIO/V C OM M WDS SID/EEC T/O/VAL COL/IV TER EfOiZ Patented May 2,1972 4 Sheets-Sheet 3 kw fm hawc Mk3 omkm mm m Patented May 2, 19723,660,746

4 Sheets-Sheet 4 751 oe-2a L AA/7'/- IT/ITER CONTROL -34 0/5 A STEI'PINGMOTOR DAMPING SYSTEM This invention relates to a method and apparatusfor controlling a stepping motor and more particularly to a method andapparatus for electronically dampening a stepping motor.

At the present time the means for linearly advancing a machine element,record member, or the like has taken many forms. One mode of advancing arecord member such as a paper tape is by continuously driving the tapethrough the use of a pinch roller and capstan arrangement. In this typeof drive, the capstan is usually precisely controlled in order to drivethe record member or tape at a constant linear speed to provide faithfulreproduction of the information stored on the record member.Accordingly. the use of such a capstan drive is considered relativelyexpensive. The capstan drive has also been employed for incrementallyadvancing a record member. A less expensive arrangement for linearlydriving a machine element or record member is through the use of astepping motor. The stepping motor is energized at preselected intervalsto cause the motor rotor to step or incrementally advance a preselectedincrement. The selected increment of rotation of the motor rotor isrelated to the desired incremental advancement of the driven element.When employing a stepping motor, however, it is necessary to providesome means for dampening the oscillations or hunting of the motor rotorthat results from actuating or stepping the rotor. When the rotorarrives at its new position in response to the energization of a statorwinding it will produce an oscillation of decreasing intensity withtime. This undesirable action will be transmitted to the driven memberthat is coupled to the motor. Accordingly, some mechanical means ofdampening the rotor has been conventionally employed with the steppingmotor. There is also presently known an electronic means for dampeningthe stepping motor. The presently known electronic means for dampeningthe stepping motor consists of causing the rotor to be actuated in adirection opposite to the desired direction of travel towards its newposition during the advancement of the rotor to its new position. Thiselectronic means of dampening is known as retro-torque and has beenfound to have limited application. Accordingly, at the present time theapplications for a stepping motor may be greatly expanded if someeconomical arrangement can be provided for electronically dampening thestepping motor, without mechanical dampening.

The present invention provides an improved method and apparatus forelectronically dampening a stepping motor that allows the motor to beoperated at its maximum response time and which is more reliable thanpresent day capstan drive arrangements let alone other stepping motors.The method and apparatus for electronically dampening a stepping motoras provided by this invention is less expensive than other knownelectronic dampening means and less expensive to embody in present dayequipment than the capstan drive.

The method of the present invention is directed to the controlling of astepping motor including a rotor and a stator having a plurality ofenergizable windings spaced around the rotor for incrementally rotatingor stepping the rotor in response to the energization of the individualstator windings. The method includes the steps of sequentiallyenergizing the individual stator windings to cause the rotor to advanceby magnetically snapping into alignment with the energized individualwinding and thereby incrementally rotating the rotor. The rotor willadvance in a direction controlled by the sequential energization of thestator windings. During the interval an individual winding is energized,momentarily energizing all of the windings of the stator for a timeinterval sufficient to prevent the rotor from producing oscillationsupon arriving at its desired position. The selected individual statorwinding is energized before the momentary energization of the remainingwindings of the stator and maintained in energization for a preselectedtime interval thereafter to cause the rotor to incrementally advance inthe desired direction.

The control apparatus for implementing the method of the presentinvention includes a source of control signals for providing outputsignals occurring at a rate related to the desired rate of advancementof a driven element, the driven element is coupled to be driven by thestepping motor in response to counting means coupled to be responsive tothe control signals from said source and providing output signals to theindividual energizable windings of the stator for actuating or rotatingthe motor rotor in accordance therewith. In ad dition, winding controlmeans coupled to be responsive to the control signals from the source ofcontrol signals is adapted to provide an output signal to all of theenergizable winding means of the motor for an interval coincident withthe energization of the individual windings for a time interval toeffect the necessary dampening of the rotor in its advancement fromposition to position. The counting means may be a binary counterassociated with a binary decoder for decoding the pattern of outputsignals from the counting means to cause an individual winding to beenergized in accordance with the count and the plurality of windings tobe sequentially energized in accordance with the count pattern providedby the counting means.

These and other features of the present invention may be more fullyappreciated when considered in the light of the following specificationand drawings, in which:

FIG. 1 is a block diagram of the control apparatus embodying the presentinvention;

FIG. 2 is a partial, developed view of the stepping motor employed inFIG. 1 and illustrating the time relationship of the signals from thecounting means and the phase decoder for energizing the stator windingsof the stepping motor; and

FIG. 3 is a schematic circuit diagram of the control ap paratus of FIG.1.

Before examining the implementation of the stepping motor, a briefdescription of the structure and operation of the stepping motor willfacilitate the understanding of the inven tion. The stepping motor underconsideration for the purpose of the present invention is ofconventional construction and includes a rotor having a plurality ofmagnetic poles defined thereon and a stator having a correspondingplurality of energizable windings spaced around the rotor for definingstator poles when energized. The windings defined magnetic polescoacting with the poles of the rotor to cause the rotor to traveltowards the stator pole and snap in alignment therewith. The statorwindings are further arranged into groups of different phases fordefining the stator poles so that the adjacent windings of each groupdefine magnetic poles of opposite polarity and the windings of the samephase in each group are electrically connected together. Accordingly,with the energization of an individual winding of a group, all of thesame windings in the other groups are energized and with the sequentialenergization of the winding of each group the stator poles are definedin advance of the pole on the rotor to cause the rotor pole tosuccessively snap into alignment with the stator poles and therebyincrementally advance the rotor. In this conventional stepping motor, itis the actuation of the rotor to advance it to a new position thatproduces the hunting or oscillation that limits the application of thestepping motor. A more complete disclosure of the stepping motorstructure is found in the publication Control Engineering" for JanuaryI958, page 85, and the references cited therein.

The present invention can be better appreciated if the method ofcontrolling the stepping motor is first investigated. For this purpose,reference will be first made to FIG. 2 wherein a stepping motor 10 isdiagrammatically represented. In FIG. 2 the rotor 11 and the stator 12of the motor it) are illustrated in partial, exploded form to betterappreciate the relationship of the magnetic poles for the rotor and thestator. For this purpose it will be noted that the rotor poles arespaced opposite to the stator windings and that the one rotor pole, thepole identified as the pole 11A is spaced across from the correspondingstator winding 12A and in alignment with the stator pole. The rotor pole11B, illustrated to the left of the rotor pole 11A, is shown out ofalignment with its corresponding stator pole and in a position advancedto the right, or leading,

with respect to the stator pole. In the same fashion, the rotor pole 11Carranged on the opposite side of the pole 1 1A is in a laggingrelationship with respect to the corresponding stator pole. The poles Band 11C may be leading and lagging by approximately one-third of atoothwidth so that when a pole, such as the pole 11A, is magneticallysnapped into alignment with the coacting energized stator pole, theadjacent rotor poles will overlap the stator teeth by the two-thirdstoothwidth in accordance with the illustrated stepping motor structure.

The stator 12 is illustrated with individual windings 12B, 12A and 12Carranged from left to right and opposite the corresponding rotor poles118, "A and 11C, as illustrated. One terminal of each winding isconnected to a positive source of power, while the other terminal ofeach winding is illustrated connected to a power amplifier forcontinuously energizing one of the windings. The windings of the stator12 are divided into groups of three and each winding 12A, 12B and 12Chas a connection to a similar winding in the other groups defining thestator windings in accordance with the selected number of increments ofrotation desired for the stepping motor. It will be assumed that thestepping motor of the present invention can be incremented with theenergization of a stator winding. Accordingly for a complete revolutionof the rotor ll, 24 steps or increments are required resulting in eightgroups of three windings each. The method of the present inventionincludes sequentially energizing the windings 12B, 12A and 12C to causethe rotor to sequentially magnetically align itself with the energizedstator winding defining a magnetic pole coacting therewith. For example,if the stator winding 12B is considered the phase 1 winding, the 12Awinding as the phase 2 winding, and the 12C winding as the phase 3winding, the action of the rotor ll with the sequential energization ofthe three phases can be better examined. If the rotor pole 11A ispositioned to the left of the stator winding 12B, and it is desired tostep the rotor ll into alignment with the phase 1 winding, it will benecessary to energize the winding 12B of the stator. At this time itshould be noted that the magnetic poles defined on the opposite sides ofan energized winding are of the opposite magnetic polarity from thatdefined by the energized winding. With the energization of the winding[28 the magnetic pole created by the energization of the winding willcause the rotor 11 to rotate so that the pole llA aligns itself with thestator pole defined by the winding 12B. Accordingly, when the windingl2B is de-energized and the winding 12A is energized the rotor 11 willbe advanced, once again, so that rotor pole 11A will align itself withthe pole associated with the stator winding HA. In the same fashion thepole llA will be advanced opposite the phase 3 winding when the winding12C is energized. The same action occurs within each of the groups ofthe stator windings so that the rotor is magnetically urged intorotation in accordance with the energization of the individual windingof the stator to produce the desired increments of rotation. It will, ofcourse, be appreciated that the direction of the rotation of the rotorwill be in accordance with the direction of sequential energization ofthe stator windings. For example, in the above illustration, thewindings were energized from left to right causing the rotor 11 torotate advance counter-clockwise. The energization of the statorwindings in the reverse order will cause the rotor 11 to rotateclockwise.

in the aforementioned discussion of the snapping of the rotor intoalignment with a corresponding stator pole it can be appreciated thatthere is a jittering or oscillation of the rotor as a result of theactuation of the rotor. Accordingly, any driven elements coupled to therotor shaft will hunt in response thereto. To prevent such jitteringaction the method of the present invention includes the step ofenergizing the windings on the opposite side of the selected individualenergized winding corresponding to the desired position of the rotor. Asillustrated in FIG. 2, for example, if the winding 12A has beenenergized during this time, and the rotor tooth 11A is advancing towardsthe phase 2 winding, the windings 12B and [2C are momentarily energized.The windings 12B and 12C are energized along with the winding 12A for atime interval that has been determined to eliminate the jittering oroscillating of the rotor as it snaps into alignment with the energizedstator pole. in a specific embodiment, the adjacent windings I28 and 12Care energized at a time when the rotor pole 1 1A is approximatelyone-fourth of the distance to its final position in alignment with thestator pole for phase 2. At this time the winding 12B and 12C areenergized and it is though that this energization eliminates the usualoscillation associated with the rotor assuming a new position. As aconsequence of this electronic dampening action it has been found thatthe response time of the stepping motor 10 will be increased so thatthere is practically no overshoot when stepping the rotor from positionto position.

Now referring to FIG. 1, the system for implementing the methoddescribed hereinabove can be examined. The system illustrated in FIG. 1embodies the invention as it may be employed for the purposes ofincrementally linearly advancing a record member 20. For this purpose, arecord member is illustrated in the form of a paper tape having aplurality of longitudinally aligned, spaced apart feed holes 20Arecorded thereon. The record member 20 is arranged with a light source21 on one side thereof for illuminating the record member 20 and aphoto-sensor 22 arranged on the opposite side of the record member andproviding an electrical or the feed hole signal, FH, in response to thesensing of the feed holes 20A. The feed hole signals, then, will beemployed as control signals for the circuit means that control thestepping motor 10. The record member 20 is linearly and incrementallyadvanced by means ofthe stepping motor 10. For this purpose, thestepping motor 10 will be provided with a sprocket wheel 23 coupledthereto to be rotatable with the motor rotor and with the sprocket teeth23A in engagement with the feed holes 20A of the record member 20. Itshould be appreciated, then, with each increment of rotation of therotor shaft, the sprocket wheel 23 will rotate in unison therewith andthereby linearly advance the record member 20 in response to therotation of the sprocket wheel 23. With the particular motor [0 underconsideration, an increment of [5 is equivalent to one-tenth of an inchlinear advancement of the tape 20.

The energization of the stator windings of the stepping motor 10 isproduced through the provision of a bi-directional counter 24. Thecontrol system is constructed and defined so that the bi-directionalcounter 24 is responsive to the clock pulses provided by the clock pulsegenerator 25. The direction of the count for the counter 24 iscontrolled by a direction command signal from the source of directioncommands 26. The direction command signal controls the counter 24 sothat it either counts up or counts down in accordance with the desireddirection of travel of the record member 20, i.e., to the right or tothe left. The bi-directional counter 24 produces a count pattern inresponse to each clock pulse coupled thereto and the pattern of thecounter 24 is decoded by means of a phase decoder 27 coupled to receivethe output pattern of signals from the counter 24 and provide a signalfor energizing an individual winding of the stator 12 for the steppingmotor 10. The decoded signals from the phase detector 27 are coupled tothe stepping motor 10 by means of an OR gate 28.

The clock pulse generator 25 comprises an OR gate 29 for receiving thesignals from the source of direction commands 26 and provides an outputsignal to an AND gate 30. The AND gate 30 is also connected to beresponsive to the feed hole signal through the advancing or step ratecircuit 31 and an OR gate 32 coupled to the output of the circuit 31.The output of the AND gate 30 is coupled to trigger a pulse generator 33which provides clock pulses at a rate related to the desired rate oftravel of the record member 20. The clock pulses are derived from theterminal identified as the CP ter minal and which terminal has a leadwire coupled to the counter 24.

The arrangement of eliminating the jittering action of the rotor 11 byproducing the momentary energization of all of the stator windings isproduced by the anti-jitter control element identified by referencenumber 34. The anti-jitter control 34 is responsive to a clock pulsefrom the generator 25 and provides an output signal to the OR gate 28for actuating all of the windings of the stator 12 of the stepping motor10.

The advancing or step rate circuit 31 is illustrated as including apulse generator 31A coupled to be responsive to the feed hole signal FH.The pulse generator 31A is controllable to provide pulses to the OR gate32 at a rate for controlling the rate of advancement of the recordmember 20. In particular, the advancing or step rate circuit element 31may be employed for controlling the rate of travel of the record memberduring the time that the information recorded on the record member 20 isbeing read or sensed. For the rewinding operation, when no informationis being sensed, it is desired to quickly return the record tape 20 tothe left-hand spool at the completion of a reading operation, duringwhich time the tape was advanced from left to right. To this end, acircuit element 35, identified as the fast rewind element, is coupled tobe responsive to the feed hole signal. This element 35 bypasses thestep-rate circuit 31 and triggers the clock pulse generator to operateat a high repetition rate for rapidly advancing the record member 20.The rewind or reading speeds may be selected by means of a modeselection switch, diagrammatically illustrated as a switch 36 connectedto the outputs of the step-rate circuit 31 and the fast rewind circuit35.

With the above structure in mind, the operation of the structure of FIG.1 can now be examined in detail. It will be assumed that it is desiredto advance the record member 20 from left to right for reading orsensing the tape 20 and accordingly the switch 36 is placed in the readmode and the source of direction commands 26 is actuated so that thedirection command signal coupled to the bi-directional counter 24controls it to count up. It will also be assumed in accordance with therepresentations of FIG. 2, that the capacity of the counter 24 is threecounts so that each of the phases for a group of windings for the stator12 will be sequentially energized in accordance with the count of thecounter 24. The counter 24 will be considered to initially read ()0. Inthis condition, the winding [2B or the phase 1 winding will beenergized. At this time, the rotor ll will be aligned with the phase 1winding of the stator 12 and the pole defined by the energization of thewinding [28 to incrementally advance the record member 20. With theapplication of the command signal to the circuit a clock pulse will begenerated for the advancement of the record member 20. This will countup the counter 24 and its output pattern will now signal 10. Thispattern will be decoded by the decoder 27 and the resulting outputsignal will energize the winding 12A with the advancement of the recordmember 20, the next feed hole 20A will be sensed so that the sensor 22will provide an output signal to the step-rate circuit 31, and in turnby means of the OR gate 32 and the AND gate the pulse generator 33 istriggered. The clock pulse provided by the pulse generator 25 is coupledto the counter 24 to count up the counter so that its output patternwill now read 01. This will cause the phase decoder 27 to decode thispattern so that the signal derived from the OR gate 28 will energize thephase three winding or the winding 12C for the stator 12.

During each of the winding energization periods and a preselectedinterval after the generation of a clock pulse, a pulse will be derivedfrom the anti-jitter element 34 in response to the clock pulse. Thispulse will occur during the interval that the rotor is advancing betweenpositions and will be effective for energizing windings 12A, 12B and 12Cmomentarily. Upon the termination of the signal from the antijittercontrol element 34, the winding 12A is maintained energized to allow therotor 11 to position itself without jittering. With the advancement ofthe rotor 11A, the record member 20 is also advanced and so another feedhole signal is generated for counting up the counter 24. During thisthird phase the counter will read 0 l and the phase 3 winding will beenergized along with the subsequent energization of the antijittercontrol element 34. Following the advancement of the record member 20the counter will be set to its initial state, reading 0 0 and the cyclewill continue with each group of three phase windings being sequentiallyenergized for advancing the tape 20 from left to right. It will beappreciated that with a left command coupled from the command source 26the counter will be counted down to cause the rotor to rotate in theopposite direction to thereby advance the record member 20 from right toleft.

Now referring to FIG. 3, the detailed structural organization of thecontrol apparatus of the present invention will be examined. The sourceof direction commands 26, illustrated in FIG. 3 in block form, commandsthe control circuitry to drive the record member 20 to the right or tothe left in accordance with the direction of travel which the userdesires, as in the previous embodiment. In the event that the inventionis employed in a paper tape reader the drive to the right can beconsidered as the reading mode, and the drive to the left can beconsidered as the rewind mode. The signal derived from the commandsource 26 may be a pulse signal which would incrementally advance therecord member 20, or the distance between the feed holes 20A. The recordmember 20 may be continuously driven whereby the feed hole signals willcontinuously function to incrementally advance the record member 20. Thedirection command is applied to the bidirectional counter 24 to controlthe direction of the count as signalled by the direction commandappearing on the lead wire 40.

The bi-directional counter 24 is constructed and defined by two bistableelements which may be flip-flops and are identified as the elements F1and F2. The set" input for the elements F1 and F2 are arranged with anexclusive OR circuit 24-] for the element F1 and an exclusive OR circuit24-2 for the element F2. The bistable elements F1 and F2 can beconsidered to be J-K flip-flops so that the K input is always TRUE or isconnected to a positive source of potential, as illustrated. Theremaining inputs to the elements F1 and F2 are the clock pulse inputsidentified as CP. The two complimentary outputs of the bistable elementsFl an d F2 are identified in conventional fashio as the F1 and F1outputs for the F] element, and F2 and F2 for the F2 element. Thedirection command signal from the lead wire 40 is coupled to each of theexclusive OR circuits 24-1 and 24-2 as one input signal to each of thesegating elements. The remaining input for the exclusive OR circuit 24-1is the F2 output signal from the element F2, while the remaining inputto the exclusive OR circuit 24-2 is the FT output signal from theelement Fl. The count capacity of the counter 24 is defined to have amaximum capacity of three counts and the elements F] and F2 areinitially set to indicate a zero count and provide an output pattern of00.

The signal from the source of direction commands 26 is also applied toan OR gate 29 which in turn has its output circuit connected to a threeinput AND circuit 30. In addition to the input from the OR circuit 29the two inputs to the AND gate 30 comprise the signals for operating thecontrol apparatus in either the "read mode or the "fast rewind" mode inaccordance with a selection of the mode by the user through theoperation of mode selector switch 36. This structure will be describedin detail immediately hereinafter. The output signal from the AND gate30 is coupled to the clock pulse generator 25 that provides a clockpulse from its CP output terminal that has a repetition rate inaccordance with the desired rate of linear travel for the record member20. The clock pulse generator may be of any conventional constructionand as illustrated in FIG. 3 comprises two serially arranged NOR gates25-1 and 25-2. The NOR circuit 25-] receives the output signal from theAND gate 30. The output of the NOR gate 25- 1 is connected as an inputto the NOR gate 25-2. The clock pulse driven from the CP terminal of theclock pulse generator 25 is coupled to each of the elements identifiedas having a corresponding CP input terminal such as the elements F1 andF2 of the bi-directional counter 24.

As will be appreciated by those skilled in the art, each count signalledby the counter 24 provides a different output pattern of signals as aresult of the switching of the elements F1 and F2 of the counter 24.This pattern of signals is decoded by the decoding element 27 comprisingthree NAND gates 27-1, 27- 2 and 27-3. The NAND gates 27-1, 27-2 and27-3 are defined for providing an output signal to an individual statorwinding of the stepping motor 10. In particular, the NAND circuitsdefine an energizing signal for the respective phases 1, 2 and 3 of thewindings identified by the reference letters 12A, 12B and 12C. For thispurpose the phase decoder 27 is defined so that the NAND circuit 27-1has as input signals the signals fi and F2. When these input conditionsare met then the phase 1 winding will be energized. The NAND circuit27-2 has as its input signals for providing a winding energizing signalto the phase 2 windings, the signals F1 and E2. The phase 3 windings areenergized through the NAND circuit 27-3 when the signals F l and F2occur at this gate. Each of the NAND circuits for the phase decoder 27are coupled to an individual OR gate comprising the OR gate 28. For thispurpose OR gate 28-] is coupled to receive the signals from the NANDcircuit 27-1, while the OR gate 28-2 receives the output signals fromthe NAND gate 27-2 and the signals from the gate 27-3 is coupled to ORcircuit 28-3. The output for each of the individual circuits 28-1, 28-2and 28-3 are connected to a power amplifying circuit that is responsiveto the output signals from each of the OR gates for amplifying thesesignals and energizing the individual windings. The power amplifiers areshown as two stages of power transistor amplifiers connected to anindividual stator winding. The power amplifiers are further identifiedas the phase l, phase 2 and phase 3 power amplifiers in accordance withthe windings that are to be energized therefrom. The power amplifiersare of conventional construction and need not be further considered forthe purposes of this invention.

The step-rate circuit 31 is coupled to be responsive to the feed holesignal which is identified as the feed hole signal (Fl-l) for providingthe necessary pulse for triggering the clock pulse generator 25. Thefeed hole signal is coupled through a pulse generator by means of atransistor amplifier. The pulse generator is of the same generalconstruction as the clock pulse generator 25 in that it is constructedof a pair of NOR gates 31-1 and 31-2 arranged in serial fashion fordefining a pulse repetition rate in accordance with the rate for whichthe feed hole signals FH are received. For this purpose the feed holesignal is derived from the input amplifier as one input signal to theNOR gate 31-]. The other input signal being connected to a source ofpositive potential and in common with one of the input circuits for theNOR gate 31-2. The other input to the NOR gate 31-2 is coupled to theoutput circuit for the NOR gate 31-1. At this point it should be notedthat the output circuit for the NOR circuit 31-2 further includes anoutput signal identified as FH'. This FH signal is coupled to the inputof the AND gate 35F and will be considered hereinafter. The outputcircuit from the NOR circuit 31-2 is connected through an RC circuitfurther identified as a window". The provision of the window" allows theuser to advance the record member 20 from to approximately 250characters per second. For this purpose, if the input signal goes FALSE50 microseconds after it went TRUE and less than 2 microseconds afterthe next feed hole is sensed, the one-shot multivibrator 31-0/8 coupledto the RC circuit will not be triggered. This action occurs if the levelof the signal on lead wire 31CP goes FALSE and thereby inhibits thetriggering of the one-shot multivibrator 3l-0/S in accordance with theaforementioned time limits. The one-shot multivibrator 31-0/S isadjustable and provides a variable continuous advance rate. One of theoutput terminals of the one-shot is identified as the OSl output, whilethe other output is identified as 051.

The fast rewind circuit 35 is defined to bypass the advancing orstep-rate circuit 31 and apply the FR signals directly to the clockpulse generator 25. The circuit 35 is defined to provide a clock pulserepetition rate of a higher rate than that provided from the circuit 31.For this purpose the mode selection switch 36 would be placed in therewind mode. The fast rewind circuit 35 comprises an inverter 35]coupled to ground when the rewind position is selected by means of themode selector switch. The inverter 351 has its output connected to anAND circuit 35F. The other input to the AND circuit 35F is the FM signalderived from the step-rate circuit 31 and mentioned hereinabove. Theoutput of the AND gate 35F is coupled as one input to the AND circuit30. ln the same fashion when the circuit is operating in the read mode,an AND circuit 31R is utilized and it has one input connected in commonwith the input signal to the inverter 351. The remaining input to theAND circuit 31R is the OSI signal from the one-shot multivibrator of thestep-rate circuit 31. The output of the AND circuit 31R is the remaininginput to the three input AND gate 31.

The anti-jitter control circuit 34 comprises a one-shot element that iscoupled to be responsive to the clock pulse provided from the generator25. The output of the one-shot element 34 is identified as the Ofioutput. The one-shot element is defined to provide a preselected timedelay in response to a clock pulse signal that allows the stator windingenergized by the phase decoder 27 to be energized and after apreselected time later the 082 signal is derived from the anti-jittercontrol circuit 34 and is coupled in common to each of the OR circuits28-1 and 28-2 and 28-3. Accordingly, a pulse will appear at the outputof each of these OR circuits for a preselected time interval that willcause all of the windings for each of the phases to be energized inaddition to the energization of the selected winding to eliminate theconventional hunting problem.

With the above structure in mind and with specific reference to FIG. 3.the detailed operation of the control circuit for the stepping motor 10will be examined. It will be assumed that the counter is in the 0 countand that the elements F1 and F2 read 00. The output pattern for thethree counts of the counter and the corresponding wave forms derivedfrom the counter and phase decoder are illustrated in FIG. 2. Inparticular, the counter 24 will signal the patterns 0 0, l O, and 0 lfor energizing the phases 1, 2 and 3 windings respectively in countingfrom 0 to 2. It will now be assumed that the direction command will bein the positive direction or for moving the tape right to left and thatthe tape is being advanced in the read mode. Under these conditions, thephase 1 winding, winding 12B, will be energized.

In order to step the rotor 11 to the next position the source ofdirection commands 26 will be activated. It will be recognized that thesource of direction commands will be actuated either by means ofa switcharranged on the front panel of the control apparatus that is operable bya user or the signals may be automatically provided with some associatedcontrol circuitry. With the initiation of the command signal the clockpulse generator 25 will be activated as a signal will be provided fromthe AND circuit 30. At this time, the input to the inverter 35] is notgrounded and with the reception of the signal OS] from the step-ratecircuit 31, the AND circuit 31R will have its input conditions satisfiedand will provide a TRUE signal to the AND gate 30. The output signalfrom the AND gate 35F will be TRUE at this interval and will be coupledto the AND circuit 30. This, then, will provide a signal from the ANDcircuit 30 for generating a clock pulse. Thus clock pulse will count thecounter 24 up one count so that the counter elements will signal 1 0.With this count prevailing the input signals to the NAND circuit 27-2will be satisfied so that the OR gate 28-2 will activate the 4J2 poweramplifier for energizing the winding 12A. This will cause the rotor 11to begin its advance to the next position. During the interval that therotor 11 is advancing, the clock pulse will also be coupled to theanti-jitter control element 34 so that a preselected interval after theenergization of the winding 12A, a pulse will appear for a preselectedinterval at the 082 output of the element 34. This signal will becoupled to each of the OR gates 28-1, 28-2 and 28-3 and thereby to allof the windings for the stator of the step motor 10 to momentarilyenergize them. Subsequently,

with the deenergization of all of the windings except the phase 2winding, or winding l2-A, the rotor 11 will continue to its new positionand magnetically snap into alignment with the corresponding stator polewithout any jitter. With the advancement of the tape to a new positionthe feed hole signal FH will be generated and is applied to the pulsegenerator 31A for triggering the element 31-0/S of the step-rate circuit31. The signal 31CP will trigger the clock pulse generator 25 to providethe next clock pulse for counting up the counter 24 to advance the rotorto the next position. This advancement will occur when the phase 3windings or the winding 12C is energized. As in the previous step aselected interval after the clock pulse is generated the 6 signal willappear and will be effective for energizing all of the windings of thestator and allow the rotor to advance positively to the next position.This action continues so that the counter output pattern will nextsignal l in response to the next clock pulse and then on the 3rd clockpulse will return to the setting 00 and cycle in the same fashion forcontinuously stepping the record member 20.

What is Claimed is:

1. Control apparatus for a stepping motor comprising a plurality ofenergizable windings for advancing the rotor in response to thesequential energization of the stator windings, and

circuit means for sequentially energizing the stator windings foradvancing the rotor in response to the energization thereof,

said circuit means including further circuit means for momentarilyenergizing all of the stator windings for a preselected time intervalless than the time period required to advance the rotor from position toposition and while the rotor is advancing from one position to the next,the preselected time interval being of a duration to electrically dampthe rotor upon arrival at said next position.

2. Control apparatus for a stepping motor as defined in claim I, whereinthe circuit means includes counting means for providing output controlsignals for controlling the sequential energization of the statorwindings and signal control means for stepping the counting means fromcount to count.

3, Control apparatus for a stepping motor as defined in claim 2, whereinsaid further circuit means comprises time delay means for providing asignal of a said preselected time interval for energizing all of thestator windings.

4. Control apparatus for advancing a record member, said apparatuscomprising motor means adapted for advancing a record member coupledthereto, said motor means including a plurality of energizable windingmeans and a rotor, the energization of an individual winding meanscausing the advancement of the rotor and a record member coupledthereto,

a source of control signals for providing output signals occurring at arate related to the desired rate of advancement ofa record member,

counting means coupled to be responsive to the output signals from saidsource and providing output signals coupled to the energizable windingmeans for sequentially energizing the individual winding means foractuating the motor rotor in accordance with the count thereof, and

winding control means coupled to be responsive to the control signalsfor providing an output signal to each of the energizable winding meansfor an interval less than the time required to advance the rotor fromposition to position and in coincidence with the energization by thecounting means of said individual winding means for damping the rotor inits advancement from position to position.

5. Control apparatus for incrementally advancing a record member havingcontrol information recorded thereon, and including means for sensingthe control information as the record member advances and providing acontrol signal at each preselected increment of advancement of therecord member, the improvement comprising stepping motor means coupledto the record member and adapted for linearly advancing the recordmember at said preselected increments. the motor means including astator having individually energizable windings and a rotor magneticallycoupled to the stator and responsive to the energization of theindividual windings for rotating said preselected increment,

binary signal generating means coupled to be responsive to the controlsignals derived from the record member and providing binary signals inresponse thereto, binary counting means coupled to be responsive to thebinary signals for providing output signals coupled to individualwindings of the motor means in accordance with each count thereof forthe duration of the count, and

anti-jitter control means coupled to be responsive to the binary signalsfor providing a winding energization signal of a preselecte durationless than the time period required to advance the rotor from position toposition and at a preselected interval after the energization of theindividual windings by the counting means to all of the winding means,the preselected interval being defined for reducing the oscillation ofthe rotor at each increment of advancement for positively advancing therecord member.

6. Control apparatus for incrementally advancing a record member asdefined in claim 5, wherein the binary counting means includes binarydecoding means for decoding the pattern of output signals from thebinary counting means for energizing the individual windings of themotor means in a predetermined sequence for linearly advancing therecord member.

7. Control apparatus for incrementally advancing a record member asdefined in claim 6, wherein the record member has a plurality oflongitudinally aligned feed holes for generating the control signalscorresponding to each of the feed holes, and the motor means includes asprocket wheel coupled to he rotatable with the motor rotor and engaginga feed hole for advancing the record member with the advancement of therotor, said binary signal generating means including means forcontrolling the repetition rate of the binary signals in ac cordancewith the desired rate of advancement of the record member.

8. Control apparatus for incrementally advancing a record member asdefined in claim 7, wherein the counting means is a bi-directionalcounter and includes means for controlling the direction of counting inaccordance with the desired direction of travel of the record member.

9. Control apparatus for incrementally advancing a record member asdefined in claim 7, wherein the means for controlling the repetitionrate of the binary signals includes means for controlling the rate ofadvancement of the record member for sensing the information on therecord member and means for controlling the rate of advancement withoutsensing the record member.

10. A method of controlling a stepping motor including a rotor and astator having a plurality of energizable windings spaced around therotor for incrementally rotating the rotor in accordance with theenergization of the stator windings, the method including the steps ofsequentially energizing an individual winding of the stepping motor tocause the rotor to magnetically snap into alignment with the energizedwinding and thereby incrementally rotate the rotor in accordance withthe sequential energization of the windings, and

during the interval an individual winding is energized and while therotor is advancing between stator poles momentarily energizing all ofthe windings of the stator for a time interval less than the time periodrequired to advance the rotor from position to position and ofsufficient time duration to prevent the rotor from hunting.

ll. A method of controlling a stepping motor including a rotor having aplurality of magnetic poles defined thereon and a stator having acorresponding plurality of energizable a preselected interval after anindividual winding of each group is energized and during the time therotor is advancing between stator poles, energizing the adjacentwindings of each group for a preselected interval less than the timeperiod required to advance the rotor from position to position, and

maintaining the energization of said individual windings after thepreselected interval to cause the rotor to incrementally advance withoutproducing settling in oscilla trons.

1. Control apparatus for a stepping motor comprising a plurality ofenergizable windings for advancing the rotor in response to thesequential energization of the stator windings, and circuit means forsequentially energizing the stator windings for advancing the rotor inresponse to the energization thereof, said circuit means includingfurther circuit means for momentarily energizing all of the statorwindings for a preselected time interval less than the time periodrequired to advance the rotor from position to position and while therotor is advancing from one position to the next, the preselected timeinterval being of a duration to electrically damp the rotor upon arrivalat said next position.
 2. Control apparatus for a stepping motor asdefined in claim 1, wherein the circuit means includes counting meansfor providing output control signals for controlling the sequentialenergization of the stator windings and signal control means forstepping the counting means from count to count.
 3. Control apparatusfor a stepping motor as defined in claim 2, wherein said further circuitmeans comprises time delay means for providing a signal of a saidpreselected time interval for energizing all of the stator windings. 4.Control apparatus for advancing a record member, said apparatuscomprising motor means adapted for advancing a record member coupledthereto, said motor means including a plurality of energizable windingmeans and a rotor, the energization of an individual winding meanscausing the advancement of the rotor and a record member coupledthereto, a source of control signals for providing output signalsoccurring at a rate related to the desired rate of advancement of arecord member, counting means coupled to be responsive to the outputsignals from said source and providing output signals coupled to theenergizable winding means for sequentially energizing the individualwinding means for actuating the motor rotor in accordance with the countthereof, and winding control means coupled to be responsive to thecontrol signals for providing an output signal to each of theenergizable winding means for an interval less than the time required toadvance the rotor from position to position and in coincidence with theEnergization by the counting means of said individual winding means fordamping the rotor in its advancement from position to position. 5.Control apparatus for incrementally advancing a record member havingcontrol information recorded thereon, and including means for sensingthe control information as the record member advances and providing acontrol signal at each preselected increment of advancement of therecord member, the improvement comprising stepping motor means coupledto the record member and adapted for linearly advancing the recordmember at said preselected increments, the motor means including astator having individually energizable windings and a rotor magneticallycoupled to the stator and responsive to the energization of theindividual windings for rotating said preselected increment, binarysignal generating means coupled to be responsive to the control signalsderived from the record member and providing binary signals in responsethereto, binary counting means coupled to be responsive to the binarysignals for providing output signals coupled to individual windings ofthe motor means in accordance with each count thereof for the durationof the count, and anti-jitter control means coupled to be responsive tothe binary signals for providing a winding energization signal of apreselecte duration less than the time period required to advance therotor from position to position and at a preselected interval after theenergization of the individual windings by the counting means to all ofthe winding means, the preselected interval being defined for reducingthe oscillation of the rotor at each increment of advancement forpositively advancing the record member.
 6. Control apparatus forincrementally advancing a record member as defined in claim 5, whereinthe binary counting means includes binary decoding means for decodingthe pattern of output signals from the binary counting means forenergizing the individual windings of the motor means in a predeterminedsequence for linearly advancing the record member.
 7. Control apparatusfor incrementally advancing a record member as defined in claim 6,wherein the record member has a plurality of longitudinally aligned feedholes for generating the control signals corresponding to each of thefeed holes, and the motor means includes a sprocket wheel coupled to berotatable with the motor rotor and engaging a feed hole for advancingthe record member with the advancement of the rotor, said binary signalgenerating means including means for controlling the repetition rate ofthe binary signals in accordance with the desired rate of advancement ofthe record member.
 8. Control apparatus for incrementally advancing arecord member as defined in claim 7, wherein the counting means is abi-directional counter and includes means for controlling the directionof counting in accordance with the desired direction of travel of therecord member.
 9. Control apparatus for incrementally advancing a recordmember as defined in claim 7, wherein the means for controlling therepetition rate of the binary signals includes means for controlling therate of advancement of the record member for sensing the information onthe record member and means for controlling the rate of advancementwithout sensing the record member.
 10. A method of controlling astepping motor including a rotor and a stator having a plurality ofenergizable windings spaced around the rotor for incrementally rotatingthe rotor in accordance with the energization of the stator windings,the method including the steps of sequentially energizing an individualwinding of the stepping motor to cause the rotor to magnetically snapinto alignment with the energized winding and thereby incrementallyrotate the rotor in accordance with the sequential energization of thewindings, and during the interval an individual winding is energized andwhile the rotor is advancing between stator poles momentarily energizingall of The windings of the stator for a time interval less than the timeperiod required to advance the rotor from position to position and ofsufficient time duration to prevent the rotor from hunting.
 11. A methodof controlling a stepping motor including a rotor having a plurality ofmagnetic poles defined thereon and a stator having a correspondingplurality of energizable windings spaced around the rotor, the windingsbeing divided into spaced groups of different phases for defining statorpoles with the adjacent windings of each group arranged for definingpoles of opposite polarity and the windings of the same phase in eachgroup being connected together whereby the sequential energization ofthe stator windings in each group causes the rotor to magnetically alignwith the energized winding and the stator pole defined thereby toincrementally rotate the rotor, the method including the steps ofsequentially energizing an individual winding of each group forincrementally advancing the rotor, a preselected interval after anindividual winding of each group is energized and during the time therotor is advancing between stator poles, energizing the adjacentwindings of each group for a preselected interval less than the timeperiod required to advance the rotor from position to position, andmaintaining the energization of said individual windings after thepreselected interval to cause the rotor to incrementally advance withoutproducing settling in oscillations.